Field of the Invention
The present disclosure relates to an organic light emitting display device.
Discussion of the Related Art
Due to advantages of compactness and light weight, flat panel displays (FPDs) have been widely used in portable computers or portable cellular terminals such as notebook computers, personal digital assistants (PDAs), as well as in monitors of desktop computers. FPDs include a liquid crystal display (LDD), a plasma display panel (PDP), a field emission display (FED), and an organic light emitting display device.
Among the FPDs, an organic light emitting display device has a fast response speed, expresses brightness with high luminous efficiency, and has a wide viewing angle. In general, in an organic light emitting display device, a data voltage is applied to a gate electrode of a driving transistor using a switching transistor turned on by a scan signal, and an organic light emitting diode (OLED) emits light using the data voltage supplied to the driving transistor. That is, a current supplied to the OLED is adjusted by the data voltage applied to the gate electrode of the driving transistor. Here, however, driving transistors respectively formed in pixels have threshold voltages Vth with variations. Due to the variations of the threshold voltages of the driving transistors, a current value different from a designed value may be supplied to the OLED, and thus, brightness may be different from a desired value.
In order to compensate for the variation of the threshold voltage of a driving transistor, various methods have been proposed. One of these methods is compensating for the variation of the threshold voltage of a driving transistor using a sampling operation of saturating a gate-source potential of the driving transistor with a threshold voltage.
As for the sampling operation, it is important to secure a sufficient time to saturate the gate-source potential of the driving transistor with the threshold voltage. However, since a horizontal period for scanning one horizontal line is shortened as the resolution of a display panel is increased, it is not easy to secure the sampling period.